It is unclear whether the large number of phenotypic changes occurring in the host cell upon viral transformation involve many cellular gene products or only a few. In addition, it is not known if these changes require the activation of inactive genes of the host cell, the modification of cellular gene products already being made, neither, or both. One way of measuring the genetic complexity of transformation is to determine how many new RNA sequences are present in transformed cells. The main purpose of the present proposal is to extend a recent observation that about 1000 nuclear RNA sequences become activated after transformation of CEF by RSV. We have identified one of these sequences as the embryonic beta globin gene. We would like to clone several of these sequences and to study their activation in terms of their transcription products and the state of the chromatin coding for them. The generality of these sequences to the "transformed state" will also be examined by assaying their activation in different cells transformed by the same virus and in smaller cells transformed by different viruses and also, by chemical carcinogens. In separate experiments, we will be analyzing revertants of polyoma transformed cells in an effort to detect a host cell suppressor of transformation. The revertants may also be cells that have lost an active chromosome conformation associated with the integrated polyoma DNA sequences. Such a revertant may yield information concerning the types of sequences required to establish a DNase I sensitive conformation.